retirement visa means you cannot work or earn income in thailand so why would you pay tax. there is a provision in thai tax laws from memory that says money earned on assets or investments in the previous year can be transferred to thailand for living expenses so this seems to be the so called loop hole, thou others will comment something differing maybe they right maybe they wrong but i can tell you with all the guys that i socialise and golf with the ones that are retired here and there are many dont pay any taxes in thailand.
we bought our dogs from singapore directly into Phuket did all the necessary paper work and they had to be micro chipped and vaccinations snd medical certificate from vet and we were allocated a 7 day window to bring them in otherwise medical certificate is invalid but had not issued people very helpful just checked their micro chips with scanner and paid 700 thb not sure what it was for maybe administration fee
David Only income earned inside Thailand shall be subjected to tax during retirement. Therefore, you will not be obliged to pay any taxes for any income you have earned from overseas. Also, personal income taxes are not required for retirees in Thailand. Note that you can't work in Thailand while on a retirement visa.
dont worry i have been asked many times for TFN and had to explain that its not applicable as we dont work here as not allowed under our visa rules....